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MiniDisc Lifespan

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zahne

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I think the long discussion above basically tries (maybe unsuccessfully) to make the point that the external properties of a device do not necessarily give an infallible guide to its construction. At this juncture I believe the properties Philippe is talking about arise out of some inherent properties of ATRAC rather than from some fundamental trickery done by the Sony engineers in this deck.

Stephen

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I think I understand thanks for the explanation.

"FROM ATRAC to CD is lossless" is lossless the best way to describe this transformation?

The point I made (and still subject to verification/proof) is that (maybe):

- starting from ATRAC you CAN get losslessly back to ATRAC (via CD quality)

- if you start from CD you cannot get losslessly back to CD (via ATRAC), because ATRAC must throw away information in order to compress the data and store it.

Clear as mud?

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The point I made (and still subject to verification/proof) is that (maybe):

- starting from ATRAC you CAN get losslessly back to ATRAC (via CD quality)

ATRAC compression/decompression is definitely lossy: sound quality audibly degrades with generations. That is true for digital and analog copies. I assume that this was an early Sony requirement, precisely to avoid identical copies of copyrighted sound material. Ironically, the W1 meets the requirement, as it slightly damages the last 1/86s of the track :-) Well done.
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  • 10 years later...

I am a dj and great fan of this format. It was a great idea. On the topic of longevity of the discs. I have recently experienced failure to record on sony " old stock" new discs. The coating on the underside seems to have degraded and shed its top surface causing Spotting.. I had others from the same stock I had recorded on previously which still play & record fine. I suspect by recording a chemical reaction takes place which stabilises the surface and strengthens it making it useable time and time again. So if you sitting on new ones you bought years ago. Record to them & rerecord when needed. Trust me , they will last longer.

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Recording spot-heats the disc, so this probably drives off any moisture that could cause oxidation of the disc surface.

The discs you experienced this with, were they still in their intact wrappers prior to the use you describe?

I've only seen this (or similar) on one disc - a TDK MXR that I'd had for many years (well since ~1999). On one part of the disc it had what looked like small rust spots on it. It would not read.

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This is a very olde thread? But one thing not mentioned by anyone is that the top surface has a lubricant to cut down on record head wear and tear. Maybe a md will stil be ok to play in 50 years time but will it still be recordable, will the  lube have dried up and damage the record head?

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I tend to lean towards that "lubricant" is more of a solid form than of a liquid or gel-like. Something similar to the teflon coatings on the "non-stick" pans.

Certainly even that could deteriorate over time, although I still owe myself an explanation, how - besides when exposed to excess heat and/or damp. (That coating on the back of the discs were claimed as a sort of silicone-based compound, and those are generally fairly stable stuff.)

I second to Kevin, none of my MD discs I have ever bought (first one back in early 1998 or so) had any trouble with recording onto, even these days, but one or two (out of ~1400-ish).

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1 hour ago, NGY said:

I tend to lean towards that "lubricant" is more of a solid form than of a liquid or gel-like. Something similar to the teflon coatings on the "non-stick" pans.

Certainly even that could deteriorate over time, although I still owe myself an explanation, how - besides when exposed to excess heat and/or damp. (That coating on the back of the discs were claimed as a sort of silicone-based compound, and those are generally fairly stable stuff.)

I second to Kevin, none of my MD discs I have ever bought (first one back in early 1998 or so) had any trouble with recording onto, even these days, but one or two (out of ~1400-ish).

not sure about it being lke teflon. I once took back a lot discs to Richer Sounds, those nice Ruby coloured one as I could see circular rings on the top silver side presumably the semi liquid lube, maybe a bit thicker than on other  discs, as the head made contact - the  magnetic  record head writes on the top side not the bottom. The laser works on the dark underside? So the lube is  some kind of silicon material? it might be quite stable but for how long?  dont know about the dark underside the laser reads - remember in the olde days of rusting cds? minidiscs  belong to those  days? Coatings have advanced eg compare cds/dvds with the almost unscratchable blu rays?

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2 hours ago, freddyjollo said:

remember in the olde days of rusting cds? minidiscs  belong to those  days?

MD-s and CD-s are two different things. Layers that hold data on recordable minidiscs and regular CD-s are two very distinct materials. Former one is a special magnetic alloy, while the latter one is a pure reflective layer of a thin metal film. Yes, some makes of early CD-s have shown oxidizing, when the plastic encapsulation was done cheaply.

As for premastered MD-s, yes, they are essentially CD-s with different encoding and track structure, while the reflective layer and the read out technology are practically the same. Yes, they might be subject of the same disease. However, we don't want to record on a premastered MD, do we.

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We're largely not interested in the top side of the disc, so long as it's not in a condition that would damage the overwrite head. All of the "magic" is the inner layers of the disc, sandwiched between polycarbonate layers for protection. The optical transparency of the underside so the laser can "see" the MO and reflective layers is key to reading the disc. During recording, the OWH creates a (relatively wide) magnetic field that permeates to the MO layer whilst the laser spot-heats to the Curie point (185degC for the alloy used in MD) from the underside to record the single binary digit at that disc location. Rinse and repeat.

Here is a diagram of the "disc sandwich" from the Minidisc Technical Primer from minidisc.org :

md_layers.PNG

Here's the statement on the OWH contact for all you "lube fan-boys":

md_lube.PNG

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5 hours ago, NGY said:

I second to Kevin, none of my MD discs I have ever bought (first one back in early 1998 or so) had any trouble with recording onto, even these days, but one or two (out of ~1400-ish).

I echo that.... the only thing that appeared to be brand-of-md-related is the report I and others made with some disks with transparent cases (the TD RXG) recording ok, but not playing back well on some other devices eg my MDX-66XLP car MD changer.

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4 hours ago, NGY said:

MD-s and CD-s are two different things. Layers that hold data on recordable minidiscs and regular CD-s are two very distinct materials. Former one is a special magnetic alloy, while the latter one is a pure reflective layer of a thin metal film. Yes, some makes of early CD-s have shown oxidizing, when the plastic encapsulation was done cheaply.

As for premastered MD-s, yes, they are essentially CD-s with different encoding and track structure, while the reflective layer and the read out technology are practically the same. Yes, they might be subject of the same disease. However, we don't want to record on a premastered MD, do we.

The point I was making is that material technology has improved since the early days of minidisc and cd not that they were similar technologys. Some of the early cd were  terrible. I have some JVC CDRs where there seems to be no protective coating on the top and you can scratch it off or it flakes off if you bend the cd!!!!! These bronzed quite quickly

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4 hours ago, kgallen said:

We're largely not interested in the top side of the disc, so long as it's not in a condition that would damage the overwrite head. All of the "magic" is the inner layers of the disc, sandwiched between polycarbonate layers for protection. The optical transparency of the underside so the laser can "see" the MO and reflective layers is key to reading the disc. During recording, the OWH creates a (relatively wide) magnetic field that permeates to the MO layer whilst the laser spot-heats to the Curie point (185degC for the alloy used in MD) from the underside to record the single binary digit at that disc location. Rinse and repeat.

Here is a diagram of the "disc sandwich" from the Minidisc Technical Primer from minidisc.org :

md_layers.PNG

Here's the statement on the OWH contact for all you "lube fan-boys":

md_lube.PNG

all but the note about removing the lube. what happens to the lube over time, every thing deteriorates over  time?

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7 minutes ago, freddyjollo said:

The point I was making is that material technology has improved since the early days of minidisc and cd not that they were similar technologys. Some of the early cd were  terrible. I have some JVC CDRs where there seems to be no protective coating on the top and you can scratch it off or it flakes off if you bend the cd!!!!! These bronzed quite quickly

I got you.

The point I tried to make was that the early days "CD-rot" has possibly nothing to do with the above mentioned recording problems on some NOS recordable MD-s - for the different materials used.

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1 minute ago, NGY said:

I got you.

The point I tried to make was that the early days "CD-rot" has possibly nothing to do with the above mentioned recording problems on some NOS recordable MD-s - for the different materials used.

it would be interesting to know if there were any developments in  the material  technology  and design with minidisc or whether it remained the same from start to finish

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15 minutes ago, freddyjollo said:

all but the note about removing the lube. what happens to the lube over time, every thing deteriorates over  time?

Yeah, translations from Japanese to English might be misleading sometimes. My interpretation is that this "lube" is not necessary anymore, because it is "built into" the top side protective layer.

But as Kevin pointed out: with or without lubrication it should not impact the recordability of an MD disc.

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7 minutes ago, freddyjollo said:

it would be interesting to know if there were any developments in  the material  technology  and design with minidisc or whether it remained the same from start to finish

I guess the core thing - the magnetic alloy, that ultimately "holds" the data - remained the same. At least I have not yet seen any indications that laser settings (wave length as well as emitted power) would have ever been different since the first commercial MD decks appearing on the market.

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8 minutes ago, NGY said:

I guess the core thing - the magnetic alloy, that ultimately "holds" the data - remained the same. At least I have not yet seen any indications that laser settings (wave length as well as emitted power) would have ever been different since the first commercial MD decks appearing on the market.

I mean the sort of things that led to bronzing cds and cdrs. presumably later cds and cdrs were made differently?

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For other readers who are wondering what we’re waffling in about, here is a Wikipedia article talking about one phenomena due to a manufacturing issue: CD bronzing

A few months back I purchased a second hand Compact Disc that seems to exhibit the above. It wouldn’t read. It was an 80’s CD from the period and ‘Made in UK by PDO’ so quite likely from the cited Philips/DuPont manufacturing plant.

I’ve not seen this particular phenomenon on an MD (I’ve a sample size of 2 for MD-CD though!).

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